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Wasiu Olanrewaju Raji Ifedolapo Gbadesere Obadare Marry Abiodun Odukoya Lukman Mobolaji Johnson 《Arabian Journal of Geosciences》2018,11(7):144
Three years after the oil spillage and pipeline explosion that claimed about 100 human lives at Ijegun Community of Lagos–Nigeria, a combination of carefully designed 2D Electrical Resistivity Profilling and Vertical Electrical Sounding methods was deployed to map and characterise the subsurface around the contaminated site. Data acquired were processed, forward modelled and tomographically inverted to obtain the multi-dimensional resistivity distribution of subsurface. The results of the study revealed high resistivity structures that indocate the presence of contaminant (oil plumes) of different sizes and shapes around the oil leakage site. These high resistivity structures are absent in the tomograms and resistivity-depth slices computed for Iyana—a linear settlement not affected by oil spillage. The five geo-electric layers and the resistivities delineated in the area are the top soil layer, 220–670 Ωm; clayey sand layer, 300–1072 Ωm; top sand layer, 120–328 Ωm; mudstone/shale layer, 25–116 Ωm and the bottom sand layer, 15–69 Ωm. The base of the first four geo-electric layers corresponds to 3.9, 8.4, 27.2 and 34.6 m respectively. The two groundwater aquifers delineated correspond to the third and fifth geo-electric layers. The top aquifer has been infiltrated by oil plumes. The depth penetrated by the oil plume decreases from 32 m to about 24 m across the survey profiles from the two ends. It was concluded that the contaminant plumes from the oil spillage are yet to be completely degraded as at the time of the study. It is recommended that the contaminated site be remediated to remove or reduce the contaminant oil in the subsurface. 相似文献
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Kolapo Peter Onifade Moshood Said Khadija Omar Amwaama Martha Aladejare Adeyemi Emman Lawal Abiodun Ismail Akinseye Praise Oluwatomisin 《Geotechnical and Geological Engineering》2021,39(8):5445-5477
Stability is the main problem in underground excavations that can result in rock-related accidents or closure of mines. This is often controlled by the geological condition of the rockmass and the in situ stress field where excavation is being carried out. Over the years, conventional support systems such as bolts, shotcrete and mesh have been the standard support systems used in difficult ground conditions to maintain stability of underground openings. The novel Thin Spray Liner (TSL) is a technology with an improvement in terms of support capabilities for difficult geological conditions. This technology is predicted to replace conventional support systems, as it offers a significant yielding capacity that is better than that of the traditional techniques of controlling strata. The performance of the TSL lies between that of shotcrete and wire mesh. The TSL has numerous advantages regarding rock reinforcement such as rapid curing period, fast application, high tensile strength, high adhesion properties that prevent movement of rock keyblocks, improved cycle times, reduction in material-handling compared to shotcrete, and a significant ability to penetrate joints. These advantages increase the allowance for mechanisation and improvement of safety in excavations. Despite various benefits of TSLs, there are shortcomings which make end-users to be sceptical about the technology. This study provides a detailed review of the mechanism, properties, composition and types, as well as the general and mining applications of TSLs. It also describes the challenges faced by the mining industry and other end-users in accepting the technology as a solution for stability issues in underground openings. In addition, some insightful suggestions are made as recommendations for future work on the development of suitable, effective and efficient thin surface rock support technology within limitations/constraints.
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Philip G. Oguntunde Babatunde J. Abiodun Gunnar Lischeid 《Meteorology and Atmospheric Physics》2012,118(1-2):95-105
Trends and periodicity analyses can provide information on climate variability inherent in a particular variable. In this study, trend tests and spectral analysis are used to examine the existence of trends and cycles in temperature series (1901–2000) of Nigeria. Periods 1901–1929 and 1942–1980 exhibited cooling trends while 1930–1941 and 1981–2000 showed warming trends. The warmest years in Nigeria were 1941, 1935, 1931 and 1987. The coldest years were 1929, 1975, 1925 and 1974. Whereas no significant trends were detected for 1901–1930 period, the standard period 1931–1960 was marked by significant cooling while 1961–1990 was marked with significant warming. Annual temperature has risen by 0.03?°C/decade during the last century. The overall warming was mostly confined to the south of 12°N especially during April and June. Changes in minimum temperature are higher than that of maximum temperature. The quasi-biennial oscillation was found in annual data for all the six zones with periods of about 2–4?years. Nigeria landscape is under strong North Atlantic Oscillation influence in dry season and under ENSO influence during wet season. Annual temperature series was also found to exhibit significant negative correlation with SOI. 相似文献
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We report on our implementation of EULAG as a dynamical core in the Community Atmospheric Model (CAM). EULAG is a non-hydrostatic, parallel computational model for all-scale geophysical flows. EULAG’s name derives from its two computational options: EULerian (flux form) or semi-LAGrangian (advective form). The model combines nonoscillatory forward-in-time (NFT) numerical algorithms with a robust elliptic Krylov solver. A signature feature of EULAG is that it is formulated in generalized coordinates. In particular, this enables grid adaptivity. In total, these features give EULAG novel advantages over the existing dynamical cores in CAM. This paper uses a series of aqua-planet simulations to demonstrate that CAM-EULAG results compare favorably with those from CAM simulations at standard CAM resolution that use current finite volume or Eulerian-spectral dynamical core options. We also show that the grid adaptivity implemented in CAM3-EULAG allows higher resolution in selected regions without causing anomalous behavior such as spurious wave reflection. 相似文献
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Ulrich?DiassoEmail authorView author&#;s OrcID profile Babatunde?J?Abiodun 《Theoretical and Applied Climatology》2018,133(3-4):647-662
This study investigates how a large-scale reforestation in Savanna (8–12°N, 20°W–20°E) could affect drought patterns over West Africa in the future (2031–2060) under the RCP4.5 scenario. Simulations from two regional climate models (RegCM4 and WRF) were analyzed for the study. The study first evaluated the performance of both RCMs in simulating the present-day climate and then applied the models to investigate the future impacts of global warming and reforestation on the drought patterns. The simulated and observed droughts were characterized with the Standardized Precipitation and Evapotranspiration Index (SPEI), and the drought patterns were classified using a Self-organizing Map (SOM) technique. The models capture essential features in the seasonal rainfall and temperature fields (including the Saharan Heat Low), but struggle to reproduce the onset and retreat of the West African Monsoon as observed. Both RCMs project a warmer climate (about 1–2 °C) over West Africa in the future. They do not reach a consensus on future change in rainfall, but they agree on a future increase in frequency of severe droughts (by about 2 to 9 events per decade) over the region. They show that reforestation over the Savanna could reduce the future warming by 0.1 to 0.8 °C and increase the precipitation by 0.8 to 1.2 mm per day. However, the impact of reforestation on the frequency of severe droughts is twofold. While reforestation decreases the droughts frequency (by about 1–2 events per decade) over the Savanna and Guinea coast, it increases droughts frequency (by 1 event per decade) over the Sahel, especially in July to September. The results of this study have application in using reforestation to mitigate impacts of climate change in West Africa. 相似文献
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Simulation of West African monsoon using the RegCM3. Part I: Model validation and interannual variability 总被引：1，自引：0，他引：1
E. A. Afiesimama J. S. Pal B. J. Abiodun W. J. Gutowski Jr A. Adedoyin 《Theoretical and Applied Climatology》2006,86(1-4):23-37
Summary The West African monsoon oscillates each year with remarkable regularity but the interannual variability associated with the
monsoon is not fully understood although much progress has been made in recent years. This study examines and evaluates the
mean state and the interannual variability of the West African climate as simulated by the International Centre for Theoretical
Physics (ICTP) Regional Climate Model version 3 (RegCM3) over the period 1979 through 1990 using the National Center for Environmental
Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis data as lateral boundary conditions.
Our analysis shows that the averaged rainfall over the region is well represented by the model and demonstrates considerable
skill in reproducing the extreme rainfall regimes.
There is however a tendency to overestimate rainfall amounts along the Guinean coast, particularly around mountainous areas,
and to underestimate it over the Soudano-Sahel. The increased rainfall along the coast is due to an enhanced low-level convergence
of the moist southwesterly winds along the coast leading to a reduction of the moisture content in the atmosphere. The decrease
over the Soudano-Sahel could be associated with the weakening of the land–sea temperature gradient and hence the decrease
in the low level southerly flows. The spatial and temporal variations in temperature are well captured by the model except
for slightly cold bias over the coastal region due to an overestimation of precipitation. 相似文献
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Emiola O. Gbobaniyi Babatunde J. Abiodun Mark A. Tadross Bruce C. Hewitson William J. Gutowski 《Theoretical and Applied Climatology》2011,106(1-2):189-210
This paper presents an evaluation of the simulated coupling between cloud base height (CBH) and surface fluxes over selected Coordinated Enhanced Observing Period (CEOP) reference stations by five regional climate models as part of a transferability intercomparison experiment. The model results are compared with station data obtained during the first phase of the CEOP measuring campaigns. The models gave a credible simulation of both diurnal and seasonal cycles of cloud base height and surface variables over the stations. However, the models exhibited some difficulty in reproducing the diurnal and seasonal temperatures over the tropical stations. The study used principal component analysis to show that three factors account for most of the variability in the observed and simulated data and to investigate the coupling between cloud base height and surface fluxes in the data. In the observations, CBH is well coupled with the surface fluxes over Cabauw, Bondville, Lamont, and Berms, but coupled only with temperature over Lindenberg and Tongyu. All models but GEMLAM simulate substantial coupling between CBH and surface fluxes at all stations; GEMLAM does not couple CBH with surface fluxes, but with surface temperature and specific humidity. 相似文献